The best resource for any compliance related question is to call your local field office. These people will be the best equipped to answer your questions, and should be familiar with any special exemptions or rules that exist in your state or the state you plan to drive through. They are easiest to reach Monday through Thursday (they should be open Fridays too) during regular business hours.
You can find the phone numbers on this website:
Here are a few popular ones:
|New Jersey||(609) 275-2604|
|New York||(518) 431-4145|
|Texas Intrastate||(512) 424-2000|